It was on a farm somewhere in southern China where the mystery pneumonia we know as SARS probably began. Once in the cities, the virus spread and - thanks to air travel - is now a flaring epidemic in more than a dozen countries. What is SARS? How did it originate? What are the symptoms? And is it treatable?

SARS, which stands for Severe Acute Respiratory Syndrome, is the
name of a potentially fatal new respiratory disease only recently recognised by
scientists. It is not the name of the micro-organism that causes the disease -
this is suspected to be a virus, although exactly which one is still uncertain.

Where did SARS come from?

The disease was first identified by Dr Carlo Urbani, an infectious
diseases specialist for the World Health Organisation who directed public health programs in Cambodia, Laos
and Vietnam. Based in Hanoi, the 46-year-old Italian epidemiologist was called
in after a visiting Chinese-American businessman, Johnny Cheng, became gravely
ill and Vietnamese doctors were mystified by the disease.

Urbani visited the man at the French Hospital in Hanoi
on 26 February 2003 and, over the next week, took many samples.
The disease looked like pneumonia - an acute disease marked by inflammation
of the lungs and usually caused by bacteria, viruses or occasionally
by chemical irritants. But the 48-year-old patient also had a high
fever, cough, shortness of breath and other symptoms that suggested
something else. Despite intensive care, Cheng eventually died -
but not before he had infected 33 hospital staff and Urbani himself,
who finally succumbed to the respiratory disease a month later.
All of Vietnam's 62 cases can be traced to the businessman, who
had arrived from Hong Kong only three days before being admitted
to the hospital.

Soon, other cases emerged in Hong Kong, and World
Health Organisation (WHO) officials began to suspect the disease
might be linked to sporadic reports from the Guangdong province
of southern China in early February that hundreds of people were
falling ill with a strange form of pneumonia. It turned out they
were right: an outbreak had begun there in November 2002, and had
now spread to Hong Kong. It was in the former British colony that
the worldwide outbreak really got its wings: thanks to the international
nature of this bustling Asian city, and its role as a trade and
transport hub for Asia, the putative disease had soon spread to
19 countries. As of 10 April 2003, there were 2,781 known cases
and 111 deaths from the new disease.

On March 19, German and Hong Kong scientists isolated in infected
patients a completely new virus from the Paramixoviridae family - known
to cause mumps and measles - which they blamed for the disease. Hailing from a
sub-group known as a metapneumoviruses, the bug was also found in the respiratory
tract of patients in Canada - home to the fourth largest number of cases. Metapneumoviruses
were themselves very new, having only recently been discovered by Dutch researchers
to cause respiratory ailments in children, and later identified as being the cause
of respiratory ailments in about 5% of children at one hospital in Brisbane, Australia.

But a week later, U.S. scientists said they had isolated another
previously unknown virus from the Coronaviridae family - known to cause
the common cold and some intestinal ailments - which they believed was the real
culprit. Canadian microbiologists also isolated the coronavirus in five of nine
patients tested. There are 13 species of the virus known, not all of them infecting
humans; they also affect cattle, pigs, rodents, cats, dogs and birds - especially
chickens.

It is possible that a combination of both viruses is needed to
generate SARS, or that some other as yet unclear interaction between one of them
and other micro-organisms cause the syndrome.

A special one-hour report on the SARS outbreak was
aired by ABC Radio National on 7 April 2003. It was a jointly produced
by The
Health Report and the Breakfast
program. You can listen to the special online by clicking on to the program sites.